• JSTS:Journal of Semiconductor Technology and Science
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• 제14권2호
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• pp.139-145
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• 2014

Control of threshold voltage ($V_T$) by ground-plane (GP) technique for planar tunnel field-effect transistor (TFET) is studied for the first time using TCAD simulation method. Although GP technique appears to be similarly useful for the TFET as for the metal-oxide-semiconductor field-effect transistor (MOSFET), some unique behaviors such as the small controllability under weak ground doping and dependence on the dopant polarity are also observed. For $V_T$-modulation larger than 100 mV, heavy ground doping over $1{\times}10^{20}cm^{-3}$ or back biasing scheme is preferred in case of TFETs. Polarity dependence is explained with a mechanism similar to the punch-through of MOSFETs. In spite of some minor differences, this result shows that both MOSFETs and TFETs can share common $V_T$-control scheme when these devices are co-integrated.

• 한국생활과학회지
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• 제18권2호
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• pp.491-500
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• 2009

This study was carried out to investigate the preference for traditional food of university students through the analysis of their daily meal types. Questionnaires were collected from a total of 197 students from December 2007 to February 2008 in Chungnam Province. The results are as follows; 148 of the respondents (73.0%) prefer Korean traditional meal as their favorite food. The significant differences are found in both gender groups and major groups (p<.05). 178 of the respondents (90.4%) answered that the traditional foods are excellent and good. However, the foods were significantly (p<.05) evaluated that major students consider them to be 'excellent' foods, while non-major students consider them to be 'good' foods. 136 of respondents (69.0%) answered that the traditional foods have beneficial influences on their health. In the survey on intake frequency of traditional meals, 137 of respondents (65.9%) have traditional foods more than twice a day. The ratio of traditional meal intake of male students is a significantly higher level (p<.05) than that of female students. Their preference for traditional rice cake, fermented rice punch, and juice mixed with fruits is a very high level of the average of 4.19, 4.22 and 4.34, respectively. The preference for Kimchi, Bulgoki, boiled beef slices, sundae and jelly was a relatively high level of the average of 4.43, 4.65, 4.14, 4.30, and 4.05, respectively. Concludingly, the research shows the majority of students enjoy korean traditional food and expect Korean food as favorite food to be developed and to be inherited.

• 대한기계학회논문집A
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• 제26권1호
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• pp.55-60
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• 2002

For the development of a new creep test technique, the availability of SP-Creep test is discussed for 1Cr-0.5Mo boiler header material. And some results are also compared with those of 2.25Cr- 1Mo steel which widely uses as boiler superheater tube. The results can be summarized as follows. The load exponents(n) obtained by SP-Creep test for 1Cr-0.5Mo steel are decreased with increasing creep temperature and the values are 15.67, 13.89, and 17.13 at 550$^{circ}C$ ,575$^{circ}C$ and 600$^{circ}C$, respectively. The temperature dependence of the load exponent is given by n = 107.19 - 0.1108T. This reason that load exponents show the extensive range of 10∼16 is attributed to the fine carbide such as M$_{23}$C$_{6}$ in lath tempered martensitic structures. At the same creep condition, the secondary creep rate of 1Cr-0.5Mo steel is lower than the 2.25Cr-1Mo steel1 due to the strengthening microstructure composed by normalizing and tempering treatments. Through a SEM observation, it can be summarized that the primary, secondary, and tertiary creep regions of SP-Creep specimen are corresponding to plastic bending, plastic membrane stretching, and plastic instability regions among the deformation behavior of four steps in SP test, respectively.y.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권10호
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• pp.438-442
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• 2005

Si nanocrystal (Si NC) memory device has several advantages such as better retention, lower operating voltage, reduced punch-through and consequently a smaller cell area, suppressed leakage current. However, the physical and electrical reasons for this behavior are not completely understood but could be related to interface states of Si NCs. In order to find out this effect, we characterized electrical properties of Si NCs embedded in a SiO$_{2}$ layer by scanning probe microscopy (SPM). The Si NCs were generated by the laser ablation method with compressed Si powder and followed by a sharpening oxidation. In this step Si NCs are capped with a thin oxide layer with the thickness of 1$\~$2 nm for isolation and the size control. The size of 51 NCs is in the range of 10$\~$50 m and the density around 10$^{11}$/cm$^{2}$ It also affects the interface states of Si NCs, resulting in the change of electrical properties. Using a conducting tip, the charge was injected directly into each Si NC, and the image contrast change and dC/dV curve shift due to the trapped charges were monitored. The results were compared with C-V characteristics of the conventional MOS capacitor structure.

• 한국해양공학회지
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• 제29권2호
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• pp.175-185
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• 2015

Jack-up type WTIV(Wind Turbine Installation Vessel) is used to avoid the effects of waves when installing wind turbines in the Southwest Sea of South Korea. During the preloading procedure, unexpected penetration may cause some risks such as excessive penetration or punch-through failure. To ensure the safety of the WTIV during preloading, the bearing capacities should be evaluated based on the soil data at each borehole. Eight boreholes (OW-1 to -8) have been drilled in the Southwest Sea of South Korea. The bearing capacities of a spudcan designed to be used in this district are calculated using both a conventional analysis and finite element analysis with the soil properties of OW-1 to -8. A finite element analysis is carried out for OW-1, -3, and -4 to gain an in-depth understanding of the soil behavior during the penetration. OW-1, -3, and -4 are representative boreholes for a strong layer overlying a soft layer, a general soft layer, and a soft layer overlying a strong layer, respectively. The resultant bearing capacity curves versus the depth of the numerical analysis are compared with the conventional method. The results show that the conventional analysis is conservative. Case studies for different spudcan areas and shapes are also conducted to seek an appropriate spudcan type for the Southwest Sea of South Korea. Finally, a spudcan with a rectangular shape and a bearing area of $112.8m^2$ is selected.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.3667-3671
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• 2015

PCB(Printed circuit board) 장착을 주목적으로 하는 포밍공정에서 주름을 발생시키지 않으면서, 실험을 통하여 재료의 두께 변화를 고찰하였다. 실험결과 제 1공정의 포밍 높이는 제 2공정에서의 재료두께 변화에 크게 영향을 미치는 것으로 나타났으며, 제 1공정에서 다이의 입구 모서리는 제품높이 50%정도의 라운드를 가져야 하며, 포밍의 높이는 원래의 제품보다 재료의 두께만큼 높게 하여야 한다. 또한 제 1공정에서 포밍형상을 구현하면 재료의 두께가 85%로 얇아지고 제 2공정에서 리스트라이킹시 재료의 두께가 80%로 얇아진다. 그러므로 정확한 형상을 구현하기 위해서는 재료가 얇아지는 것을 고려하여 다이는 원제품의 형상을 유지하고 펀치는 원제품의 깊이에 재료 두께의 20%이상 더한 값만큼 길이를 길게 하여야 압축의 효과를 얻을 수 있다.

• Archives of Plastic Surgery
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• 제36권5호
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• pp.519-524
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• 2009

Purpose: This study was conducted to establish the most effective method of cell therapy by comparing and analyzing the level of wound healing after various cell delivery methods. Methods: Human mesenchymal stem cells were administered using 5 different methods on full thickness skin defects which were deliberately created on the back of 4 - week old mice using a 8 mm punch. Different modes of administration, cell suspension, local injection, collagen GAG matrix seeding, fibrin, and hydrogel mix methods were used. In each experiment group, $4{\times}105$ mesenchymal stem cells were administered according to 5 deferent methods, and were not for the corresponding control group. Results: The wound healing rate was fastest in the local injection group. The wound healing rate was relatively slow in the collagen matrix group, however, the number of blood vessels or VEGF increased most in this group. Conclusion: For rapid wound healing through wound contraction, it is advantageous to administer MSC by the local injection method. For the healing process of a wide area, such as a burn, the seeding of cells to collagen matrix is thought to be effective.

• 대한기계학회논문집A
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• 제37권1호
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• pp.67-75
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• 2013

핵연료 지지격자 소재로 사용되는 zircaloy-4의 유동응력을 Johnson-Cook 모델로 결정하고, 모델의 재료상수를 역 공학으로 도출했다. 변형률 항의 상수 A, B, n과 변형률 속도 항의 $\dot{\varepsilon}_0$은 인장시험을 통해 결정했다. 상수 C, m을 역 공학으로 도출하기 위해 슬롯밀링시험을 수행하고, 유한요소해석으로 모사했다. 실험과 해석으로 얻은 결과의 차이를 오차함수, 즉 최소화 대상 목적함수로 설정했고, 이 함수를 최소로 하는 C, m을 도출했다. 도출한 상수의 타당성을 검증하기 위해 상관계수를 살펴봤고, 전단시험과 해석을 수행해 교차 검증했다. 상관계수는 모든 조건에 대해 0.97이상으로 실험과 해석결과 사이에 강한 상관관계가 있음을 확인했다. 전단시험과 해석의 전단면 형상 및 최대하중을 비교하여 도출한 유동응력 모델이 타당함을 보였다.

• 한국응용곤충학회지
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• 제51권4호
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• pp.383-388
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• 2012

본 연구는 여름기간동안 대파에서 파좀나방 밀도에 따른 피해수준을 분석하고, 해충관리의 기초자료인 경제적피해수준을 제시하고자 수행되었다. 2009년부터 2010년까지 수원지역 대파 재배포장에서 성페로몬 트랩을 이용한 성충 발생 모니터링 결과, 3~5월, 9월에 특히 많은 개체가 채집되었다. 파좀나방의 가해양상은 유충이 잎을 뚫고 들어가 내부에서 갉아먹으면 잎 표면이 초록빛을 잃고 하얗게 변하였고, 구멍이 생겨났다. 유충 1마리가 전체 유충기간동안 평균 1.6개 잎을 가해하였고, 11.9개의 구멍을 냈으며 피해면적은 $1,321.6mm^2$에 달했다. 망사케이지에 파좀나방 유충을 밀도수준별로 접종한 결과, 파좀나방 밀도수준에 따라 파의 평균 엽수의 감소와 피해엽률의 증가에 따라 총 수량 및 상품수량이 감소되었다. 피해해석 결과, 해충밀도와 피해엽률간에는 고도로 유의한 정(+)의 상관관계가 있는 회귀식을 구할 수 있었다. 이 식을 이용하여 대파의 상품화율 93%를 감안하여 설정한 피해한도인 피해엽률 7% 수준에서 파좀나방의 경제적 피해수준은 10주당 유충 1마리로 추정되었다.

• Asian-Australasian Journal of Animal Sciences
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• 제23권4호
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• pp.430-436
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• 2010

The objective of the present studies was to develop and validate a system for isolation, purification and extended culture of pigment-producing cells in alpaca skin (melanocytes) responsible for coat color and to determine the effect of alpha melanocyte stimulating hormone treatment on mRNA expression for the melanocortin 1 receptor, a key gene involved in coat color regulation in other species. Skin punch biopsies were harvested from the dorsal region of 1-3 yr old alpacas and three different enzyme digestion methods were evaluated for effects on yield of viable cells and attachment in vitro. Greatest cell yields and attachment were obtained following dispersion with dispase II relative to trypsin and trypsin-EDTA treatment. Culture of cells in medium supplemented with basic fibroblast growth factor, bovine pituitary extract, hydrocortisone, insulin, 12-O-tetradecanolphorbol-13-acetate and cholera toxin yielded highly pure populations of melanocytes by passage 3 as confirmed by detection of tyrosinase activity and immunocytochemical localization of melanocyte markers including tyrosinase, S-100 and micropthalmia-associated transcription factor. Abundance of mRNA for tyrosinase, a key enzyme in melanocyte pigment production, was maintained through 10 passages showing preservation of melanocyte phenotypic characteristics with extended culture. To determine hormonal responsiveness of cultured melanocytes and investigate regulation of melanocortin 1 receptor expression, cultured melanocytes were treated with increasing concentrations of ${\alpha}$-melanocyte stimulating hormone. Treatment with ${\alpha}$-melanocyte stimulating hormone increased melanocortin receptor 1 mRNA in a dose dependent fashion. The results demonstrated culture of pure populations of alpaca melanocytes to 10 passages and illustrate the potential utility of such cells for studies of intrinsic and extrinsic regulation of genes controlling pigmentation and coat color in fiber-producing species.